A DFT Mechanistic Study of the trans-[OsVIO2(OH)4]2– and [OsVIIIO4(OH)n]n− (n = 1, 2 cis) Comproportionation Proton-Coupled Electron Transfer Reaction

Herein, we present a DFT computational study of the trans-[OsVIO2(OH)4]2– and [OsVIIIO4(OH)n]n− (n = 1, 2 cis) comproportionation reaction mechanism that occurs in a basic aqueous matrix. The reaction pathway where [OsVIIIO4(OH)]− reacts with trans-[OsVIO2(OH)4]2– via an intermediate mediated concerted electron–proton transfer yielded the best agreement with experiment (Δ‡H°, Δ‡S° and Δ‡G° experimental data for the forward reaction are 10.3 ± 0.5 kcal mol–1, −2.6 ± 1.6 cal mol–1 K–1, and 11.1 ± 0.9 kcal mol–1 and for the reverse reaction are −6.7 ± 1.0 kcal mol–1, −63.6 ± 3.4 cal mol–1 K–1, and 12.2 ± 2.0 kcal mol–1, respectively, where at the PBE-D3 level for the forward reaction are 11.3 kcal mol–1, −9.8 cal mol–1 K–1, and 14.2 kcal mol–1 and for the reverse reaction are −11.8 kcal mol–1, −80.7 cal mol–1 K–1, and 12.3 kcal mol–1, respectively) and consists of (i) formation of a (singlet spin state) noncovalent adduct, [OsVIII═O···HO—OsVI]3–, (ii) spin-forbidden, concerted electron–proton transfer (i-EPT...